<PAGE>
 
                                                                      EXHIBIT 10


                              FIRST AMENDMENT TO
                     AMENDED AND RESTATED CREDIT AGREEMENT


     THIS FIRST AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT (this "First
Amendment"), dated as of September 15, 1997, is entered into among CompUSA Inc.,
a Delaware corporation ("Borrower"), the banks listed on the signature pages
hereof (collectively, the "Lenders"), and NationsBank of Texas, N.A., as
Administrative Lender (in said capacity, the "Administrative Lender").


                                  BACKGROUND
                                  ----------

     A. Borrower, Lenders and Administrative Lender heretofore entered into that
certain Amended and Restated Credit Agreement, dated as of December 30, 1996
(the "Credit Agreement"; the terms defined in the Credit Agreement and not
otherwise defined herein shall be used herein as defined in the Credit
Agreement).

     B. Borrower, Lenders and Administrative Lender desire to make an amendment
to the Credit Agreement.

     NOW, THEREFORE, in consideration of the covenants, conditions and
agreements hereinafter set forth, and for other good and valuable consideration,
the receipt and adequacy of which are all hereby acknowledged, Borrower, Lenders
and Administrative Lender covenant and agree as follows:


     1.         AMENDMENTS TO CREDIT AGREEMENT.
                ------------------------------ 

     (a) Section 7.6 of the Credit Agreement is hereby amended to read as
follows:

         "Section 7.6  Restricted Payments.  The Borrower shall not, and shall
                       -------------------                                    
     not permit any Subsidiary to, directly or indirectly declare, pay or make
     any Restricted Payments; provided, however, (a) any Subsidiary may declare
     and pay Dividends to the Borrower or another Subsidiary, (b) the Borrower
     may make loans to directors, officers and employees of Borrower and its
     Subsidiaries during any Fiscal Year (calculated net of loan repayments),
     together with the Guaranty of Indebtedness of directors, officers and
     employees permitted pursuant to Section 7.5 hereof during such Fiscal Year,
                                     -----------                                
     in an aggregate amount not to exceed $1,000,000, (c) the Borrower may
     prepay the Senior Subordinated Notes in part or in full, and (d) the
     Borrower may make Treasury Stock Purchases of its shares of capital stock
     for an aggregate consideration not to exceed $130,000,000; provided,
     further, however, the Borrower shall not pay or make any such Restricted
     Payment set forth in clause (b), (c) or (d) above unless there shall exist
     no Default prior to or after giving effect to any such proposed Restricted
     Payment."
<PAGE>
 
     (b) The Compliance Certificate is hereby amended to be in the form of
                                                                          
Exhibit C attached to this First Amendment.
---------                                  

     2.   REPRESENTATIONS AND WARRANTIES TRUE; NO EVENT OF DEFAULT.  By its
          --------------------------------------------------------         
execution and delivery hereof, Borrower represents and warrants that, as of the
date hereof and after giving effect to the amendments contemplated by the
foregoing Section 1:

     (a) the representations and warranties contained in the Credit Agreement
and the other Loan Documents are true and correct on and as of the date hereof
as made on and as of such date;

     (b) no event has occurred and is continuing which constitutes a Default;

     (c) Borrower has full power and authority to execute and deliver this First
Amendment and the Credit Agreement, as amended hereby, and this First Amendment
and the Credit Agreement, as amended hereby, constitute the legal, valid and
binding obligations of Borrower, enforceable in accordance with their respective
terms, except as enforceability may be limited by applicable debtor relief laws
and by general principles of equity (regardless of whether enforcement is sought
in a proceeding in equity or at law) and except as rights to indemnity may be
limited by federal or state securities laws; and

     (d) no authorization, approval consent, or other action by, notice to, or
filing with, any governmental authority or other Person, is required for the
execution, delivery or performance by Borrower of this First Amendment or the
acknowledgement of this First Amendment by any Guarantor.

     3.  CONDITIONS OF EFFECTIVENESS.  This First Amendment shall be effective
         ---------------------------                                          
as of September 15, 1997, subject to the following:

     (a) Administrative Lender shall have received counterparts of this First
Amendment executed by Determining Lenders;

     (b) Administrative Lender shall have received counterparts of this First
Amendment executed by Borrower and acknowledged by each Guarantor; and

     (c) Administrative Lender shall have received, in form and substance
satisfactory to Administrative Lender and its counsel, such other documents,
certificates and instruments as Administrative Lender shall require.

     4.  GUARANTOR ACKNOWLEDGEMENT.  By signing below, each of the Guarantors
         -------------------------                                           
(i) acknowledges, consents and agrees to the execution and delivery of this
First Amendment, (ii) acknowledges and agrees that its obligations in respect of
its Subsidiary Guaranty are not released, diminished, waived, modified, impaired
or affected in any manner

                                     - 2 -
<PAGE>
 
by this First Amendment or any of the provisions contemplated herein, (iii)
ratifies and confirms its obligations under its Subsidiary Guaranty, and (iv)
acknowledges and agrees that it has no claims or offsets against, or defenses or
counterclaims to, its Subsidiary Guaranty.

     5.  REFERENCE TO THE CREDIT AGREEMENT.
         --------------------------------- 

     (a) Upon the effectiveness of this First Amendment, each reference in the
Credit Agreement to "this Agreement", "hereunder", or words of like import shall
mean and be a reference to the Credit Agreement, as amended by this First
Amendment.

     (b) The Credit Agreement, as amended by this First Amendment, and all other
Loan Documents shall remain in full force and effect and are hereby ratified and
confirmed.

     6.  COSTS, EXPENSES AND TAXES.  Borrower agrees to pay on demand all costs
         -------------------------                                             
and expenses of each Lender in connection with the preparation, reproduction,
execution and delivery of this First Amendment and the other instruments and
documents to be delivered hereunder (including the reasonable fees and out-of-
pocket expenses of counsel for each Lender with respect thereto and with respect
to advising each Lender as to its rights and responsibilities under the Credit
Agreement, as amended by this First Amendment).

     7.  EXECUTION IN COUNTERPARTS.  This First Amendment may be executed in
         -------------------------                                          
any number of counterparts and by different parties hereto in separate
counterparts, each which when so executed and delivered shall be deemed to be an
original and all of which taken together shall constitute but one and the same
instrument.

     8.  GOVERNING LAW:  BINDING EFFECT.  This First Amendment shall be
         ------------------------------                                
governed by and construed in accordance with the laws of the State of Texas and
shall be binding upon Borrower and each Lender and their respective successors
and assigns.

     9.  HEADINGS.  Section headings in this First Amendment are included
         --------                                                        
herein for convenience of reference only and shall not constitute a part of this
First Amendment for any other purpose.

     10. ENTIRE AGREEMENT.  THE CREDIT AGREEMENT, AS AMENDED BY THIS FIRST
         ----------------                                                 
AMENDMENT, AND THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN
THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS,
OR SUBSEQUENT ORAL AGREEMENTS BETWEEN THE PARTIES.  THERE ARE NO UNWRITTEN ORAL
AGREEMENTS BETWEEN THE PARTIES.


                  ==========================================
                  REMAINDER OF PAGE LEFT INTENTIONALLY BLANK
                  ==========================================

                                     - 3 -
<PAGE>
 
      IN WITNESS WHEREOF, the parties hereto have executed this First Amendment
   as the date first above written.

                              CompUSA Inc.



                              By: Robert Gary
                                 -------------------------
                                 Name: Robert Gary
                                       -------------------
                                 Title: VP Finance
                                        ------------------

                                     - 4 -
<PAGE>
 
                              NATIONSBANK OF TEXAS, N.A., as Administrative
                              Lender and as a Lender



                              By: Sharon M. Ellis
                                 --------------------------
                                 Name: Sharon M. Ellis
                                      ---------------------
                                 Title: Vice President
                                       --------------------

                                     - 5 -
<PAGE>
 
                              BANK ONE, TEXAS, N.A.



                              By: R Rogers
                                 ------------------------
                                 Name: R Rogers
                                      -------------------
                                 Title: VP
                                       ------------------

                                     - 6 -
<PAGE>
 
                              THE BANK OF NEW YORK



                              By: Charlotte Sohn
                                 ------------------------
                                 Name: Charlotte Sohn
                                      -------------------
                                 Title: Vice President
                                       ------------------

                                     - 7 -
<PAGE>
 
                              THE BANK OF NOVA SCOTIA



                              By: F.C.H. Ashby
                                 -------------------------------------
                                 Name: F.C.H. Ashby
                                       -------------------------------
                                 Title: Senior Manager Loan Operations
                                       -------------------------------

                                     - 8 -
<PAGE>
 
                              CREDIT SUISSE FIRST BOSTON (formerly
                              Credit Suisse)



                              By: Robert N. Finnery
                                  -----------------------------
                                  Name: Robert N. Finnery
                                       ------------------------
                                  Title: Managing Director
                                        -----------------------



                              By: J. Scott Karro
                                 ------------------------------
                                 Name: J.Scott Karro
                                      -------------------------
                                 Title: Associate
                                       ------------------------

                                     - 9 -
<PAGE>
 
                              FLEET NATIONAL BANK



                              By: Thomas J. Bullard
                                 -----------------------------
                                 Name: Thomas J. Bullard
                                      ------------------------
                                 Title: Vice President
                                       -----------------------

                                     - 10 -
<PAGE>
 
                              THE FUJI BANK, LIMITED - HOUSTON AGENCY



                              By: Nate Ellis
                                 ------------------------------
                                 Name: Nate Ellis
                                      --------------------------
                                 Title: Vice President & Manager
                                       -------------------------

                                     - 11 -
<PAGE>
 
                              HIBERNIA NATIONAL BANK



                              By: Christopher B. Pitre
                                 ---------------------------------
                                 Name: Christopher B. Pitre
                                      ----------------------------
                                 Title: Assistant Vice President
                                       ---------------------------

                                     - 12 -
<PAGE>
 
                              MELLON BANK, N.A.



                              By: Marc T. Kennedy
                                 ---------------------------
                                 Name: Marc T. Kennedy
                                      ----------------------
                                 Title: AVP
                                       ---------------------

                                     - 13 -
<PAGE>
 
                              THE SAKURA BANK, LIMITED



                              By: Yoshikazu Nagura
                                 ----------------------------
                                 Name: Yoshikazu Nagura
                                      -----------------------
                                 Title: Vice President
                                       ----------------------

                                     - 14 -
<PAGE>
 
                              THE SUMITOMO BANK, LIMITED



                              By: Harumitsu Seki
                                 ------------------------------
                                 Name: Harumitsu Seki
                                      -------------------------
                                 Title: General Manager
                                       ------------------------ 

                                     - 15 -
<PAGE>
 
                              UMB BANK, N.A.



                              By: Charles J. Wolf
                                 --------------------------------
                                 Name: Charles J. Wolf
                                      ---------------------------
                                 Title: Senior Vice President
                                       --------------------------

                                     - 16 -
<PAGE>
 
                              FIRST BANK NATIONAL ASSOCIATION



                              By: David Kopolow
                                 -------------------------------
                                 Name: David Kopolow
                                      --------------------------
                                 Title: Vice President
                                       -------------------------

                                     - 17 -
<PAGE>
 
                              WELLS FARGO BANK (TEXAS), N.A.



                              By: Mary Jo Hoch
                                  -----------------------------
                                  Name: Mary Jo Hoch
                                       ------------------------
                                  Title: Vice President
                                        -----------------------

                                     - 18 -
<PAGE>
 
ACKNOWLEDGED AND AGREED:

COMPUSA HOLDINGS II INC.



By: Mark R. Walker
   ---------------------------
   Name: Mark R. Walker
        ---------------------- 
   Title: Sr. VP
         ---------------------


COMPUSA HOLDINGS I INC.



By: Mark R. Walker
   ---------------------------
   Name: Mark R. Walker
        ----------------------
   Title: Sr. VP
         ---------------------


PCs COMPLEAT, INC.



By: Mark R. Walker
   ---------------------------
   Name: Mark R. Walker
        ----------------------
   Title: Sr. VP
         ---------------------



COMPTEAM INC.



By: Mark R. Walker
   ---------------------------
   Name: Mark R. Walker
        ----------------------
   Title: Sr. VP
         ---------------------

                                     - 19 -
<PAGE>
 
COMPUSA MANAGEMENT COMPANY



By: Robert Gary
   ---------------------------
   Name: Robert Gary
        ----------------------
   Title: VP Finance
         ---------------------


COMPUSA STORES L.P.

By: COMPUSA INC., its general partner



     By: Robert Gary
        ----------------------
        Name: Robert Gary
             -----------------
        Title: VP Finance
              ----------------


COMPUSA HOLDINGS COMPANY



By: Robert Gary
   ----------------------
   Name: Robert Gary
        -----------------
   Title: VP Finance
         ----------------

                                     - 20 -